Wave motion compensating assembly for suction dredger

ABSTRACT

A Suction dredger, comprising a vessel and a conduit suspended on the vessel by means of at least one lifting cable guided over a guide pulley beared in a support, the lifting cable being connected via a dashing compensator comprising a cable length variator with a winch mounted on the vessel is improved for considerably reducing the wear of the expensive lifting cable. To this aim the support of the guide pulley of the lifting cable is suspended on the vessel by means of a support cable connected to the vessel through the cable length variator.

Koning et a1.

WAVE MOTION COMPENSATING ASSEMBLY FOR SUCTION DREDGER Inventors: Jan De Koning, 20, Soetendaal,

Amsterdam; Romke Van Der Veen, Prof. Dr. Hesselaan 21, .lutphaas, both of Netherlands Filed: Jan. 29, 1973 Appl. No.: 327,875

Foreign Application Priority Data Jan. 28, 1972 Netherlands 7201216 US. Cl 37/58, 37/72, 254/144, 254/172, 254/188 Int. Cl E02f 3/90, B66d 1/50 Field of Search 37/72, 58; 254/172, 173; 254/188, 144

References Cited UNlTED STATES PATENTS 12/1889 Callen 254/144 X 9/1961 Cleveland 254/172 UX 5/1970 Hadjidakis 37/72 X July 30, 1974 3,681,862 8/1972 De Koning et a1 37/72 X 3,734,564 5/1973 McKay et a1. 254/172 X 3,739,503 6/1973 Barker et a1. 37/72 X FOREIGN PATENTS OR APPLICATIONS 851,333 10/1960 Great Britain 37/72 Primary Examiner-Robert E. Pulfrey Assistant Examiner-Clifford D. Crowder Attorney, Agent, or Firm-John P. Snyder [57] ABSTRACT A Suction dredger, comprising a vessel and a conduit suspended on the vessel by means of at least one lifting cable guided over a guide pulley beared in a support, the lifting cable being connected via a dashing compensator comprising a cable length variator with a winch mounted on the vessel is improved for considerably reducing the wear of the expensive lifting cable. To this aim the support of the guide pulley of the lifting cable is suspended on the vessel by means of a support cable connected to the vessel through the cable length variator.

13 Claims, 3 Drawing Figures I PAIENTfinJuLsolm SHEET 10? 3 mimmmmsn sum anr WAVE MOTION COMPENSATING ASSEMBLY FOR SUCTION DREDGER The invention relates to a suction dredger comprising a vessel to be anchored during sucking up ground from a bottom lying under water and a flexible conduit suspended on the vessel by means of at least one lifting cable guided over a guide pulley beared in a support, said flexible conduit having a nozzle to be inserted into the bottom, said lifting cable being connected via a dashing compensator comprising a cable length variator with a winch mounted on the vessel.

This known suction dredger has the disadvantage, that each long, mostly thick and heavy lifting cable, which must adjust a part of the suction pipe under water, moves during each movement of the vessel owing to a sea level movement over the guide pulley resulting in that this expensive lifting cable is exposed to a quick wear, particularly with the dashing compensator. When substituting said lifting cable each time the operations of sucking up ground are stopped. The invention improves the known suction dredger in this respect, in that the support of the guide pulley of the lifting cable is suspended on the vessel by means of at least one support cable connected to the vessel through the cable length variator. Owing to compensating the dashing in the suspension device of the guide pulley of the lifting cable, said lifting cable is not considerably shifted with respect to the guide pulley with a sea level movement, so that only the vessel moves with the waves and the suction pipe remains nearly at its place then together with the guide pulley and the lifting cable.

For adjusting the nozzle preferably two lifting points of the nozzle axially spaced from each other are suspended on the vessel by means of separate guide pulleys beared in separate supports. Said supports can be suspended then on the vessel by means of separate support cables which are connected with the vessel via separate cable length variators.

If for adjusting the nozzle two lifting points of the nozzle axially spaced from each other are suspended on the vessel by means of two guide pulleys which are beared on places spaced from each other in a common support constituting a tongue, one winch and one dashing compensator may suffice for suspending the two guide pulleys compensated against dashing.

The invention will be elucidated in the following description with reference to a drawing.

In the drawing:

FIGS. 1, 2 and 3 each schematically represent a suction dredger according to the invention being each time further developed.

The suction dredger 20 of FIG. 1 comprises a vessel 1 which is anchored by means of anchoring cables 21 during sucking up ground, e.g., sand from a bottom 9. The suction dredger 20 comprises further a flexible conduit 3, mainly consisting of a flexible tube, in which flexible conduit 3 a pump 5 positioned under water 18 and a pump 22 positioned in the vessel 1 are mounted. The conduit 3 has a nozzle 6 to be inserted into the bottom 9 which is connected via a bridge part 23 with an outlet 8 of a pump 7 pumping water 18 into the bottom 9. The nozzle 6 of the conduit 3 is suspended on the vessel 1 by means of a lifting cable engaging the bridge part 23 and guided over a guide pulley ll rotatably beared in a support 24 and which lifting cable 10 is wound partly upon a winch drum 25 of a winch l3.

The guide pulley l1 and its support 24 constitute part of a wave motion compensating assembly including the compensator l6 piston/cylinder arrangement 26. The assembly 26 consists of a hydraulic cylinder 27 communicating via a conduit 28 with an air barrel or pneumatic accumulator 30, which is filled to such an extent with liquid 29 and air 31, that the upward pressure upon the piston 32 is sufficient for taking up the force in the lifting cable 10. The support 24 is suspended on the vessel 1 by means of a support cable 14, said support cable 14 running over a guide pulley 15 being rotatably beared in a frame 2 and said support cable 14 running via the compensator 16 while being attached to an eye 17 of the vessel 1. The support cable 14 carries nearly the same weight as the lifting cable 10. The support cable 14 is guided over a stationary rotatable pulley 33 and over a movable pulley 34 rotatably beared on the piston 32.

If the nozzle 6 sticks in the bottom 9, each lifting cable 10 keeps about the same position with respect to the guide pulley 11, but the support cable 14 will move with respect to its guide pulleys 15, 33 and 34, while the piston 32 chooses such a position, that the support cable 14 remains tightly and the vessel 1 may follow the sea level movement while the nozzle 6 and the support 24 remain nearly at a same place. When the nozzle 6 moves on behalf of the suction process the winch 13 is veered, so that the suction mouth 19 of the nozzle 6 moves then deeper into the bottom 9. For compensating the sea level movement the piston 32 moves against the air locked in the air barrel 30, so that the wave motion compensator 16 veers or hauls support cable 14, while the guide pulley l 1 can nearly stand still with respect to the nozzle 6. It is to be remarked that the lifting cable 10 can be one single thick cable or can consist of a number of rather thick cables, because said lifting cable 10 does not move so frequently, whereas the support cable 14 preferably consists of a number of rather thin cables which run parallelly side by side because said support cable 14 runs frequently over guide pulleys 34, 33 and 15.

Each suction dredger of FIGS. 2 and 3 is identical to the suction dredger 20 of FIG. 1 with the understanding that said suction dredger differs from the suction dredger 20 as far as is described below.

The flexible conduit 3 consists of three rigid tube parts 3a, 3b and 6 being swingably connected with each other by means of hinges 35, namely a tube part 3a communicating with the pump 22, a nozzle 6 carrying a suction mouth 19 and a tube part 3b lying between said tube parts 3a and 6. The nozzle 6 is adjusted by means of two separate lifting cables 10, which engage two lifting points 36 of the nozzle 6 lying axially from each other.

Each-lifting cable 10 of FIG. 2 is controlled independently by means of a winch l3 and is suspended by means of a support cable 14 via separate compensators 16 in the same way as the lifting cable 10 of FIG. 1. On

the contrary the supports 24 of the guide pulleys 11 are combined to one single, common support 24 constituting a tongue. The guide pulleys 11 are positioned on a distance from each other. This support 24 is again suspended on the vessel 1, just like the support 24 of FIG. 1, by means of a support cable 14 via a compensator 16.

In the suctiondredger 20 of FIGS. 2 and 3 the tube part 3a is suspended on the vessel 1 by means of a lift- 3 ing cable 37 via a motion compensator 38 and a winch 39.

When the vessel 1 of FIG. 3 moves as a result of sea level movement the frame 2 gets into the position 2' owing to which also the running of the lifting cables and the position of the support 24 are changed into the position shown with dotted lines. In that the support is constructed in such a manner, that all mutual move ments of the lifting cables 10 can be admitted in the work condition of the suction dredger while maintaining a minimum cable tension, all movements of the vessel with respect to the suction pipe 3 are compensated by the compensator 16 for the vertical movements while at the same time the lifting cables 10 are kept tightly, whereas for moving the vessel 1 forwards and rearwards with respect to the nozzle 6 inserted into the bottom 9, the support gets wobbling, during which movement the tension of the cables 10 is maintained.

In this way the sea level movements of the vessel 1 with respect to the suction pipe 3 are sufficiently compensated in the most occurring work circumstances. For moving the suction pipe 3 with respect to the vessel, e.g. owing to sucking in or to changements of the bottom, one has to control additionally the winches 13.

I claim:

1. A suction dredger assembly comprising, in combination:

a buoyant hull having winch means and suction dredging means mounted thereon, said suction dredging means including a nozzle adapted to be inserted into the bottom below said hull and a flexible conduit portion between said nozzle and the hull whereby the flexible conduit portion is free to flex as the hull rises and falls due to wave action without significantly affecting the position of said nozzle;

a wave motion compensating assembly comprising a length of motion-compensating cable secured to said hull, a first pulley fixed to said hull and over which said motion-compensating cable is trained, a support fixed to said motion-compensating cable below said pulley, and load-responsive means for paying out and reeling in said motioncompensating cable over said first pulley; and

a winch cable issuing from said winch means and connected to said nozzle to support same in desired bottom-penetrating position, and a load-bearing pulley carried by said support and over which said winch cable is trained whereby the load imposed on said winch cable is imparted to said motioncompensating cable;

said motion-compensating cable being of a length to position said load-bearing pulley to define a substantially horizontal winch cable section between such load bearing pulley and said winch means whereby minimally to travel said winch cable over said load-bearing pulley in response to paying out and reeling in of said motion-compensating cable.

2. A suction dredger assembly as defined in claim 1 including a frame mounted on said hull and projecting upwardly and outboard therefrom, said first pulley being carried by the outboard end of said frame whereby to provide a substantial length of said horizontal winch cable section.

3. A section dredger assembly as defined in claim 2 wherein said load-responsive means comprises a hydraulic piston-cylinder assembly and a pneumatic accumulator connected to the cylinder space of such asse mbly, a second pulley carried by said piston, and said motioncompensating cable being trained over said second pulley.

4. A suction dredger assembly as defined in claim 2 including second winch means mounted on said hull and a second winch cable issuing therefrom, said second winch cable being connected to said nozzle in spaced relation to the point of attachment of the firstmentioned winch cable thereto.

5. A suction dredger assembly as defined in claim 4 including a second wave motion compensating assembly associated with said second winch cable.

6. A suction dredger assembly as defined in claim 4 wherein said support carries a further pulley over which said second winch cable is trained.

7. A suction dredger assembly as defined in claim 1 wherein said load-responsive means comprises a hydraulic piston-cylinder assembly and a pneumatic accumulator connected to the cylinder space of such assembly, a second pulley carried by said piston, and said motion-compensating cable being trained over said second pulley.

8. A suction dredger assembly as defined in claim 7 including second winch means mounted on said hull and a second winch cable issuing therefrom, said second winch cable being connected to said nozzle in spaced relation to the point of attachment of the firstmentioned winch cable thereto.

9. A suction dredger assembly as defined in claim 8 including a second wave motion compensating assembly associated with said second winch cable.

10. A suction dredger assembly as defined in claim 8 wherein said support carries a further pulley over which said second winch cable is trained.

11. A suction dredger assembly as defined in claim 1 including second winch means mounted on said hull and a second winch cable issuing therefrom, said second winch cable being connected to said nozzle in spaced relation to the point of attachment of the firstmentioned winch cable thereto.

12. A suction dredger assembly as defined in claim 11 including a second wave motion compensating assembly associated with said second winch cable.

13. A suction dredger assembly as defined in claim 11 wherein said support carries a further pulley over which said second winch cable is trained. 

1. A suction dredger assembly comprising, in combination: a buoyant hull having winch means and suction dredging means mounted thereon, said suction dredging means including a nozzle adapted to be inserted into the bottom below said hull and a flexible conduit portion between said nozzle and the hull whereby the flexible conduit portion is free to flex as the hull rises and falls due to wave action without significantly affecting the position of said nozzle; a wave motion compensating assembly comprising a length of motion-compensating cable secured to said hull, a first pulley fixed to said hull and over which said motion-compensating cable is trained, a support fixed to said motion-compensating cable below said pulley, and load-responsive means for paying out and reeling in said motion-compensating cable over said first pulley; and a winch cable issuing from said winch means and connected to said nozzle to support same in desired bottom-penetrating position, and a load-bearing pulley carried by said support and over which said winch cable is trained whereby the load imposed on said winch cable is imparted to said motion-compensating cable; said motion-compensating cable being of a length to position said load-bearing pulley to define a substantially horizontal winch cable section between such load bearing pulley and said winch means whereby minimally to travel said winch cable over said load-bearing pulley in response to paying out and reeling in of said motion-compensating cable.
 2. A suction dredger assembly as defined in claim 1 including a frame mounted on said hull and projecting upwardly and outboard therefrom, said first pulley being carried by the outboard end of said frame whereby to provide a substantial length of said horizontal winch cable section.
 3. A section dredger assembly as defined in claim 2 wherein said load-responsive means comprises a hydraulic piston-cylinder assembly and a pneumatic accumulator connected to the cylinder space of such assembly, a second pulley carried by said piston, and said motioncompensating cable being trained over said second pulley.
 4. A suction dredger assembly as defined in claim 2 including second winch means mounted on said hull and a second winch cable issuing therefrom, said second winch cable being connected to said nozzle in spaced relation to the point of attachment of the first-mentioned winch cable thereto.
 5. A suction dredger assembly as defined in claim 4 including a second wave motion compensating assembly associated with said second winch cable.
 6. A suction dredger assembly as defined in claim 4 wherein said support carries a further pulley over which said second winch cable is trained.
 7. A suction dredger assembly as defined in claim 1 wherein said load-responsive means comprises a hydraulic piston-cylinder assembly and a pneumatic accumulator connected to the cylinder space of such assembly, a second pulley carried by said piston, and said motion-compensating cable being trained over said second pulley.
 8. A suction dredger assembly as defined in claim 7 including second winch means mounted on said hull and a second winch cable issuing therefrom, said second winch cable being connected to said nozzle in spaced relation to the point of attachment of the first-mentioned winch cable thereto.
 9. A suction dredger assembly as defined in claim 8 including a second wave motion compensating assembly associated with said second winch cable.
 10. A suction dredger assembly as defined in claim 8 wherein said support carries a further pulley over which said second winch cable is trained.
 11. A suction dredger assembly as defined in claim 1 including second winch means mounted on said hull and a second winch cable issuing therefrom, said second winch cable being connected to said nozzle in spaced relation to the point of attachment of the first-mentioned winch cable thereto.
 12. A suction dredger assembly as defined in claim 11 including a second wave motion compensating assembly associated with said second winch cable.
 13. A suction dredger assembly as defined in claim 11 wherein said support carries a further pulley over which said second winch cable is trained. 